| dc.description.abstract | REPRODUCTION OF E. EUGENIAE (OLIGOCHAETA)
AND THE INFLUENCE OF DIELDRIN.
The reproductive organs of the tropical vermicomposting
earthworm species Eudrilus eugeniae was investigated.
The ovaries and oviducts contain sperms, thus making it
highly probable that fertilisation is internal.
Spermatogenesis was studied at the ultrastructural level.
Spermatogonia, spermatids and mature sperm are described.
The general steps of spermatogenesis in E. eugeniae are
basically similar to those found in many other annelids.
An ultrastructural study of the mature sperm of E.
eugeniae showed an elongated sperm cell, typical of the
Oligochaeta. From SEM studies could be seen that the
sperm possesses a very long, well developed flagellum
with a typical "corkscrew" head. TEM studies showed the
presence of a characteristic vesicle-type acrosome,
cylindrical nucleus and spirally curved mitochondrion
with six lobes. The flagellum have a typical 9+2 micro-tubule
arrangement.
During the present study the influence of the
organochlorine, dieldrin, on the reproduction of E.
eugeniae was investigated. This was done by exposing
adult, clitellate specimens to the toxin. The contact
filter paper method was used, and a number of replicates
of the worms were exposed for 48 hours to concentrations
of 0,154; 0,462; 0,77 and 1,54μg/cm-2 of dieldrin. The
exact amounts of dieldrin which had penetrated the bodies
of the worms were determine by means of gas
chromatography.
In comparison to the "normal" spermatosoa of the control
group, no changes in sperm morphology in specimens
exposed to 0,154 or 0,462μg/cm-2 were observed. In the
sperm from the higher concentration exposures, however,
the TEM work showed definite damage to the nuclei of a
number of sperm (up to 10% in the case of the 1,54μg/cm-2
exposure). Under the SEM the sperm from the two lowest
concentrations also appeared normal, but an abnormal
curling and folding of the sperm flagella was observed in
a number of spermatosoa of the worms exposed to the
higher concentrations of dieldrin.
The gross damage observed in the nuclei of some of the
spermatosoa might directly damage the genetic material
within the spermatosoa and this could seriously influence
reproduction or cause malfunctions in offspring if these
sperm remained viable. The effect of malfunction of the
flagella on the other hand could have an effect on
fertilization. Further experimental work is, however,
needed to determine the effect of dieldrin on these
processes of reproduction. | en_US |
